﻿Public Partial Class WebForm1
    Inherits System.Web.UI.Page

    Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load

        TextBox1.Attributes.Add("Value", "1234")
    End Sub

    Protected Sub Button1_Click(ByVal sender As Object, ByVal e As EventArgs) Handles Button1.Click
        MsgBox(TextBox1.Text)
    End Sub
End Class